Potassium salts have been used to help to control the intrusion of shale and clay into fluids produced from subterranean formations. The presence of potassium in brines which come in contact with shale and clay in underground formations will inhibit the absorption of sodium into the brine from the clay or shale, thus reducing permeability damage. However, it has been difficult to determine and control the optimum amounts of potassium to use.
The use of potassium formate in formation treatment fluids containing cationic formation control additives is disclosed by Kevin W. Smith in U.S. Pat. No. 6,502,637. In U.S. Pat. No. 6,454,005, Kevin W. Smith discloses the use of potassium formate together with guar for reducing permeability damage by formation treatment fluids.
The capillary suction test is known as a method widely used to determine the tendency of clay and shale to adsorb potassium ions. Performance of a brine in the capillary suction test (CST) is used as a guide to the quantity of potassium deemed to be necessary to stabilize the formation, particularly to inhibit sloughing of shale and swelling of clay. Lauzon, in U.S. Pat. No. 4,507,210, teaches the use of the capillary suction test and/or Zeta potential to adjust or formulate a clay and shale treatment medium which may include a hydroxypropyl guar gum (column 5, lines 58–59) for minimizing swelling and dispersion of subterranean formation particles. A Zeta potential is the potential at the shear interface created by a colloidal or other particle moving through a liquid medium with its associated ions, in an electric field. Zeta potentials have been used as part of a method to extend bit life—see the review of the art in Engelmann et al. U.S. Pat. No. 5,196,401, col. 2 lines 22–36 as well as FIG. 2. Zeta potentials have been used to study clay control in the presence of polymers, in uranium mining—see Hjelmstad in U.S. Pat. No. 4,925,247.
In U.S. Pat. No. 5,489,674 to Yeh and U.S. Pat. No. 5,536,825 to Yeh et al., the authors discuss guar gum as a natural polygalactomannan. They go on to describe various derivatives of guar, including carboxymethyl hydroxypropyl guar—see column 5, line 49 of U.S. Pat. No. 5,489,674 and line 51, column 5 of U.S. Pat. No. 5,536,825. At line 23 of column 3 of Dobson et al., U.S. Pat. No. 5,629,271, carboxymethyl_hydroxypropyl guar is mentioned as a possible viscosifier and suspending agent in a “clay-free” formation treatment fluid which, however, includes an “ultra fine filtrate reducing agent.”
The full benefits of the varied elements of the prior art discussed above have yet to be realized in the well drilling and related arts.